ثُمَّ لَتَرَوُنَّهَا عَيْنَ ٱلْيَقِينِ
Thumma la-tarawunnahā ʿayna'l-yaqīn "Then you will surely see it with the certainty of seeing with the eye."
One. The eye. The organ of sight. On this reading the construct means "the certainty of the eye", that is, direct witnessing. Not what is heard but what is seen.
Two. The thing itself, its very self. In Arabic ʿayn al-shayʾ means "the very thing itself"; the words aynen ("exactly") and aynı ("the same") used in Turkish today come from this sense as well. On this reading the construct means "certainty itself" — not a degree of certainty, that is, but certainty in person.
The two senses do not conflict; they complete one another. What is seen with the eye is the thing itself.
Grammatically ʿayn al-yaqīn is in the accusative and is analysed either as an absolute object or as a circumstantial qualifier. The structure is exactly the same as ʿilm al-yaqīn in the preceding verse — which shows that the two constructs have been deliberately paired.
One — two different seeings. The first from afar, the second from close by. What is seen in the place of the gathering and what is seen when one has entered it are not the same thing. Here thumma conveys a real interval of time.
Two — emphasis. The same judgement is said a second time, this time with its quality specified. Thumma conveys distance in respect of degree.
Three — the specifying of the kind of seeing. The sixth verse announced the seeing; the seventh says in what degree of certainty that seeing will be. On this reading the second verse is like an adjective to the first.
All three can be defended. The third is supported by the deliberate repetition here of the ʿilm al-yaqīn pattern of verse 5: the sūra had named a kind of knowledge; now it names a kind of seeing.
The text describes the gulf between a man's possessing a piece of knowledge and his living according to that knowledge. It sets this down not as a moral defect but as a matter of the kind of knowledge: if the knowledge in your hand is not working, the problem lies not in its truth but in its kind.
The counterpart of this in the social sciences is real and is not forced. It is a phenomenon long discussed in psychology and the behavioural sciences: people's having correct knowledge on a subject is generally not sufficient for them to behave in accordance with that knowledge. This gap is called by various names — the knowledge–behaviour gap, the value–action gap. Its best-known examples are health behaviours: it is not an unusual situation for those who know the risks best to be the ones who take those risks most.
Various explanations are put forward as to why this should be so: that abstract knowledge carries no emotional weight; that distant consequences lose their value against near gains (the phenomenon called "temporal discounting" in economics); that risk needs to be perceived personally rather than statistically. I transmit these as attempts at explanation; none of them is settled.
But the observation itself is sound, and the description in the verse overlaps with it: that knowledge does not change behaviour until it turns into seeing. The difference of the verse is this: the modern literature defines this gap as a problem and looks for ways of closing it. The sūra says that the gap will necessarily close — and that at the moment it closes it will be too late. This is the real problem the sūra sets up.